We are interested in elucidating the mechanisms and regulation of genetic transcription in eucaryotic cells. To achieve this goal we plan to use the yeast ribosomal RNA and phenylalanine tRNA genes. We propose to identify, isolate, purify and determine the structure of the transcription components and reconstitute the process in vitro from the isolated molecules under defined conditions. Our aims include a) determination of the complete structure of the yeast ribosomal RNA and phe-tRNA cistrons and the role of the regulatory sequences adjacent to the genes themselves; b) determination of the role of each of the polypeptide components of yeast RNA polymerases in transcription, and c) identification and role of chromosomal proteins and other molecules which influence the transcription of these genes. We have isolated and purified the yeast fragments containing a particular gene to be used in in vitro transcription studies. The isolated genes will also be used in chromatin reconstitution experiments to determine the functions required for their expression. Success in these efforts would hopefully provide information about the organization and structure of ribosomal genes in eucaryotes and about the principles guiding the regulation of their expression.